Abstract
Additive manufacturing is a key enabling technology in the manufacture of highly complex shapes, having very few geometric limitations compared to traditional manufacturing processes. The present paper aims at investigating mechanical properties at cryogenic temperatures for a 316L austenitic stainless steel, due to the wide possible cryogenic applications such as liquid gas confinement or superconductors. The starting powders have been processed by laser powder bed fusion (LPBF) and tested in the as-built conditions and after stress relieving treatments. Mechanical properties at 298, 77 and 4.2 K from tensile testing are presented together with fracture surfaces investigated by field emission scanning electron microscopy. The results show that high tensile strength at cryogenic temperature is characteristic for all samples, with ultimate tensile strength as high as 1246 MPa at 4.2 K and 55% maximum total elongation at 77 K. This study can constitute a solid basis for investigating 316L components by LPBF for specific applications in cryogenic conditions.
Highlights
At present, the manufacturing of complex-shaped parts, especially if made from difficult to work metallic alloys, is a true challenge in the field of manufacturing
The dimples grown together are those responsible for load-bearing capacity of the cross-section. These data together with dimple size calculation can explain from fractography the results observed by mechanical testing
A ductilepowder fracturemetallurgy is characterized for showing a diffuse the coalescence dimples; such powder through steps, deformation to allow significant improvements in the properties of the dimples properties, are responsible forsimple the plastic occurring in the material
Summary
The manufacturing of complex-shaped parts, especially if made from difficult to work metallic alloys, is a true challenge in the field of manufacturing. AM shows the potential to substitute conventional metal manufacturing processes, such as casting and forging [3,4], mainly in the aerospace and biomedical fields. Materials 2020, 13, 3328 and reproducibility of the processes, AM competes with other progressive processes such as severe plastic deformation (SPD) [3,4,5,6,7] with substantial advantages such as the absence of constraints in the manufacturing design, shape freedom, high complexity of the components, combination of multiple parts into one part, production of functionally graded materials, reduced tooling requirements, and the possibility of production on demand [8,9,10]. A considerable amount of material can be saved by designing properly for additive manufacturing with no loss in terms of mechanical properties [11,12,13]
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